Abstract
Safety and comfort, while ensuring torque transfer capability, are essential for wet multi-plate clutches. The safety of the torque transmission process largely depends on the endurance of the tribological system against spontaneous and long-term damages. Modern Carbon friction linings in wet multi-plate clutch applications offer superior wear resistance compared to other friction materials, but there is hardly any published data on their spontaneous damage behavior. This article therefore presents results from experimental studies on the spontaneous damage of innovative Carbon friction linings carried out on a component test rig. Furthermore, the influence of different steel plate thicknesses (3.5 mm vs. 6 mm) was investigated. 16 step tests, including visual assessments of the clutches, were performed with Carbon-fiber reinforced plastic (CFRP) and Carbon-fiber reinforced Carbon (C/C) linings in brake operations.The results of the step tests are documented in friction work over friction power diagrams. Results show excellent endurance of modern Carbon friction linings against spontaneous damage and thus makes them suitable for safety relevant high-performance applications. There was no clear influence of the steel plate thickness on spontaneous damage. However, the C/C friction lining ran at a specific energy of up to 5.26 J/mm2 in combination with sliding velocities of up to 67 m/s (high speed application) without failure. This is the highest published spontaneous damage resistance identified for wet clutches.
Highlights
Wet multi-plate clutches and brakes are widely used in vehicle transmissions and industrial applications and usually fulfill safety- and comfort-relevant functions
This paper extends the knowledge through experimental investigations of spontaneous damage of two different Carbon friction materials (CFRP and Carbon-fiber reinforced Carbon (C/C))
The average Coefficient of Friction (CoF) of the C/C friction lining slightly decreases at higher loads, whereas the CoF of the Carbon-fiber reinforced plastic (CFRP) friction lining stays almost constant until failure in load stage LS10
Summary
Wet multi-plate clutches and brakes are widely used in vehicle transmissions and industrial applications and usually fulfill safety- and comfort-relevant functions. Damage of wet multi-plate clutches can originate from high mechanical and/or thermal loads and can be subdivided into spontaneous and long-term damages [1]. Numerous publications report an increase in the wear resistance [17, 18] and the coefficient of friction [18] of Carbon friction linings by introducing nanotubes into the resin material. For organic Carbon friction linings in synchronizers, the surface smoothes under high thermal loads, because oil crack products block the friction linings’ pores and reduce surface roughness [27, 28] This decreases the CoF at high sliding speeds. In addition to long-term mechanisms like wear, hot spots (spontaneous damage) occur at high temperatures in organic friction systems [31].
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